The International Association of Geomagnetism and Aeronomy (IAGA) released the 10th Generation International Geomagnetic Reference Field (IGRF) on 12 December 2004. This is the latest version of a standard mathematical description of the Earth's main magnetic field, and is used widely in studies of the Earth's deep interior, crust, ionosphere, and magnetosphere. The coefficients were finalized by a task force of IAGA, Division V, Working Group V-MODc Geomagnetic Field Modeling. The IGRF is the product of a large collaborative effort between magnetic field modelers and the institutes around the world involved in collecting and disseminating magnetic field data from satellites and observatories. The IGRF is a series of mathematical models of the Earth's main field and its annual rate of change (secular variation). The sources of the main magnetic field are electric currents in the Earth and the magnetization of crustal rocks.